This application claims the priority of German patent application 19744683, filed Oct. 9, 1997.
The invention relates to a fuel injection system for an air-compressing internal-combustion engine, particularly a supercharged engine, having an electronic control unit for a quantity adjusting mechanism for determining the injection quantity and having an electronically controlled or regulated injection timing device for changing the start of the injection in each case as a function of the operating point of the internal-combustion engine.
A fuel injection system of for a diesel internal-combustion engine is known, for example, from Schoenfelder et al., U.S. Pat. No. 5,520,152 (counterpart of German Patent Document DE 44 25 295 A1). In this known fuel injection system, a change of the injection start takes place in the form of an injection start correction as a function of the change of the rotational speed of the internal-combustion engine.
Concerning the surrounding technical field, reference is also made to German Patent Document DE 39 28 875 A1.
In the case of air-compressing internal-combustion engines, that is, particularly in the case of diesel internal-combustion engines, the fuel injection takes place while taking into account input quantities, specifically as a function of the respective engine operating point, which is generally set by means of a desired load generator, for example, in the case of motor vehicles, by means of an accelerator pedal. In this case, the desired load generator normally acts upon the quantity adjusting mechanism by means of which the injection quantity is defined, while an electronically controlled or regulated injection timing device defines the start of the injection, that is, the point in time of the fuel injection, particularly while taking into account the respective desired injection quantity.
However, in the case of previous determinations of the injection start for air-compressing internal-combustion engines, thermal conditions of the combustion space have not been taken into account. This results in disadvantages, not only with respect to the generation of noise but also with respect to emissions of the internal-combustion engine, particularly if the internal-combustion engine is intended for driving a motor vehicle.
It is an object of the invention to adapt the start of the injection to thermal conditions of the combustion space.
These and other objects have been achieved according to the present invention by providing a fuel injection system for an air-compressing internal-combustion engine, comprising: an electronic control unit for determining an injection quantity for a fuel quantity adjusting device; and an electronically controlled or regulated injection timing device for changing a starting time of a fuel injection as a function of at least one operating parameter of the internal-combustion engine, wherein the injection starting time is corrected as a function of an elapsed running time after starting of the internal-combustion engine.
These and other objects have also been achieved according to the present invention by providing a fuel injection system for an internal-combustion engine, comprising: a fuel injector; a fuel injection timing device; a fuel quantity adjusting device; and an electronic control unit controlling said fuel injection timing device and said fuel quantity adjusting device to determine a desired starting time as a function of an elapsed running time after starting of the internal-combustion engine.
These and other objects have also been achieved according to the present invention by providing a fuel injection method for an internal-combustion engine including a fuel injector, a fuel injection timing device, and a fuel quantity adjusting device, said method comprising the act of controlling said fuel injection timing device and said fuel quantity adjusting device to determine a desired starting time as a function of an elapsed running time after starting of the internal-combustion engine.
These and other objects have also been achieved according to the present invention by providing a fuel injection method for an internal-combustion engine, said method comprising the acts of: sensing when the internal-combustion engine is started; determining a standard injection start value; determining an injection start correction value as a function of an elapsed running time after the internal-combustion engine was started; and determining an actual desired injection starting time as said standard injection start value minus said injection start correction value.
According to the invention, the start of the injection is corrected as a function of the elapsed running time after the start of the internal-combustion engine.
However, preferably, the start of the injection is corrected not only as a function of the running time of the internal-combustion engine but also as a function of the coolant temperature.
Although the injection start correction can take place exclusively on the basis of the coolant temperature, it cannot be differentiated on the basis of the coolant temperature alone whether the internal-combustion engine was just started or has been in operation for a longer period of time. However, with respect to the temperature level in the combustion space, this information is of considerable importance because, even if the coolant temperature is the same, clearly different thermodynamic conditions of the combustion occur for the two cases, for the purpose of which different injection starts are desirable.
It is recommended to integrate the injection start correction, which in particular results in a late adjustment of the injection start, by means of the superimposition of characteristic correction diagrams, into the normal electronic control unit which already exists. This minimizes the implementation expenditures.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.